Metal Complexation Studies, Characterization and
Biological Activities of 1-(4-Carboxy-3-Hydroxy-N- Sec.Butyl Phenyl Amino
Methyl) Benzotriazole
P. D. Patel
Department of Chemistry, P. B. Science College, Kapadwanj-387620 (Gujarat) INDIA
*Corresponding Author E-mail: pdpatel2010@rediffmail.com
Aminomethylation
of benzotriazole was carried out by treating benzotriazole with formaldehyde
and N-sec.butyl 4-aminosalicylic acid. The resultant compound was designated as
1-(4-caroxy-3-hydroxy-N-sec.butyl phenyl amino methyl) benzotriazole (CSPB).
The transition metal complexes of Cu2+ , Co2+, Ni2+,
Mn2+and Zn2+ of CSPB have been prepared and
characterized by elemental analysis, spectral studies, magnetic moment, molar
conductivity and antimicrobial activity.
KEYWORDS: Benzotriazole, N-sec.butyl-4-aminosalicylic acid,
metal complexes, spectral studies, magnetic moment, antibacterial and
antifungal activity.
INTRODUCTION:
One
of the heterocyclic compound say 1-(H)-benzotriazole is found as an important
heterocyclic compound. It’s prime application is as corrosion inhibiters for
copper or copper alloys1,2. Ciba Geigy has introduced
benzotriazole derivative under the trade name Trinavin-p3. It is
applied as an UV light absorber for stabilizing plastics and other organic
materials against discoloration determination3. It is also employed
as photographic emulsion stabilizer4. In the peptide synthesis it
acts in form of an active ester5. The area in which the amino
methylation of benzotriazole by using aromatic amine having metal gripping
group (i.e ligand) has not been developed. Hence it was thought to undertake
such work. With this view, the present author communicated the initial work
recently6. In connection of this work the present paper describes
the synthesis and characterization of benzotriazole,
N-sec.butyl-4-aminosalicylic acid clubbed molecule and its metal complexes6-10.
The work is illustrated in Scheme-1.
EXPERIMENTAL:
Materials
Benzotriazole
was prepared by method reported in literature11.
N-sec.butyl-4-aminosalicylic acid was prepared by method reported12,13.
All other chemicals used were of analytical grade.
Synthesis
of 1-(4-carboxy-3-hydroxy-N-sec.butyl phenyl amino methyl) benzotriazole:
A
mixture of 1-H Benzotriazole (0.02 mole), formaldehyde (0.02 mole) and
N-sec.butyl-4-aminosalicylic acid (0.02 mole) in ethanol (70 ml) was heated
under refluxed for 4h. Subsequently ethanol was distilled off and the lump mass
obtained. It was triturated with petroleum ether (40-60 °C). The solid
designated as CSPB was isolated and dried in air. Yield was 60%. It’s m.p. was
198°C. (Uncorrected).
Elemental
analysis:
C18H20N4O3
(340 gm/mol)
C%
H% N%
Calculated:
63.52 5.88 16.47
Found:
63.45
5.82 16.40
IR
Features: 3028,1498,1598 cm-1 Aromatic
1699 cm-1 >CO of -COOH
3546 cm-1 -OH
2890,2920 cm-1 >CH2
NMR
7.1-7.7 ppm Multiplet aromatic
(DMSO)
2.57 ppm (2H) Singlet (> CH2)
10.0 ppm (1H) Singlet (-COOH)
3.9 ppm (1H) Singlet (-OH)
1.2 ppm (3H) Doublet (-CH3)
2.8 ppm (2H) Multiplet (>CH-)
1.52 ppm (2H) Multiplet (>CH2)
1.00 ppm (2H) Triplet (-CH3)
Synthesis
of metal complexes of CSPB:
Formation
of CSPB metal complexes:
The
Cu2+, Co2+, Ni2+,Mn2+, and Zn2+
metal ion complexes of CSPB have been prepared in a similar manner.
The procedure is as follow.
To
a solution of CSPB (0.1 mole) in ethanol-acetone (1:1) mixture (25 ml), 0.1 N KOH
solution was added drop wise with stirring. The pasty precipitates were
obtained at neutral PH. These were dissolved by addition of water up to clear
solution. It was diluted to 250 ml of the stock solution was added drop wise to
the solution of metal salt (0.005 mole ) in water at room temperature. Sodium
acetate or ammonia was added up to complete precipitation. The precipitate was
digested on water bath at 80°C for 2 h. The digested precipitates of complex
were filtered washed with water and air dried. It was amorphous powder. Yield
was almost quantitative. The details are given in Table-1.
Measurements:
The
elemental analysis for C, H, and N were carried out on elemental analyzer. IR
spectra of CSPB and its metal complexes were scanned on a Nicolet 760 FTIR
spectrophotometer in KBr. The metal content of the metal chelate were performed
by decomposing a weighed amount of each metal complexes followed by EDTA
titration as reported in literature11. Magnetic susceptibility
measurement of all the metal complex was carried out at room temperature by the
Gouy method. Mercury tetrathiocynatocobaltate (II) Hg [Co (NCS)4]
was used as a calibrant. The diffused reflectance spectra of solid metal
complex were recorded on a Beckman-DK-2A spectrophotometer with a solid
reflectance attachment, MgO was employed as the reflectance compound.
Antifungal
activity:
The
fungicidal activities of all the compounds were studied at 1000 ppm
concentration in vitro. Plant pathogenic organisms listed in Table-3 were used.
The antifungal activities of all the samples were measured by cup plate method15.
Each of the plant pathogenic strains on a potato dextrose agar (PDA) medium
contained potato 200gms, dextrose 20gms, agar 20gms, and water 1 litre, 5 days
old culture were employed. The compounds to be tested were suspended (1000 ppm)
in a PDA medium and autoclaved for 15 min. at 15 atm pressure. These
medium were poured into sterile Petri plate and the organisms were incubated
after cooling the Petri plated. The percentage inhabitation for fungi was
calculated after 5 days using the formula given below.
Percentage
of Inhibition:
100 (X-Y)
X
Where
X: Area of colony in control plate
Y: Area of colony in test plate
The
fungicidal activity all compounds are shown in Table-3.
RESULTS
AND DISCUSSION:
The
parent ligand CSPB was an amorphous yellow powdered, soluble in various
solvents like dioxane, DMSO and DMF. The results of elemental analysis of the
ligand are reported in Table-1. They are consistent with the predicted
structure as shown in Scheme-1 the ligand was synthesized as shown in the
scheme-1.
Examination
of IR spectrum (not shown) of CSPB reveals that a broad band of phenolic hydroxyl
stretching is observed at 3200-3600 cm-1 as well as additional
absorption bands at 3028 cm-1, 1598 cm-1 and 1498 cm-1
are characteristics of the salicylic acid 16-17. The strong bands at
1699 cm-1 for C=O. The NMR data (shown in experimental part) also
confirm the structure of CSPB. The metal complex of CSPB with the metal ions Cu2+,
Co2+, Ni2+, Mn2+, and Zn2+ vary in
colours. On the basics of the proposed structure as shown in schme-1, the
molecular formula of the CSPB ligand is C18H20N4O3
which upon complexion coordinates with one central metal atom at four
coordination sites and with two water molecules. Therefore the general
molecular formula of the resulting metal complex is [C36H38N8O6]
M 2(H2O) for divalent metal ions. This has been
confirmed by results of elemental analysis of all the five metal chelate and
their parent ligand. The data of elemental analysis reported in Table-1 are in
arrangement with the calculated values of C, H and N based on the above
mentioned molecular formula of parent ligand as well as metal complex.
Inspection
of IR Spectra (not shown) of metal complexes reveals that all the spectra are
identical in all respects. The comparison of IR spectrum of the parent ligand
CSPB with that of its each metal complex has revealed certain characteristics
differences.
One
of the significant differences to be expected between the IR spectrum of the
parent ligand and its metal complex is the presence of more broadened bands in
the region of 3200-3600 cm-1 for the metal complex as the oxygen of
the O-H group of the ligands forms a coordination bond with the metal ions 13-15.
This is explained by the fact that water molecules might have strongly absorbed
to the metal chelate sample during their formation.
Table-1
Analytical data of the metal chelates of CSPB
|
Compound
|
Empirical
Formula
|
Mol. Cal
Gm/mole
|
Yield (%)
|
Elemental Analysis
|
|
C%
|
H%
|
N%
|
M%
|
|
Calcd.
|
Found
|
Calcd.
|
Found
|
Calcd.
|
Found
|
Calcd.
|
Found
|
|
CSPB
|
C18H20N4O3
|
340
|
60
|
63.53
|
63.50
|
5.88
|
5.80
|
16.47
|
16.42
|
------
|
-------
|
|
[Cu(CSPB)2(H2O)2]
|
C36H38N8O6Cu2+
2(H2O)
|
777.54
|
67
|
55.56
|
55.50
|
5.40
|
5.32
|
15.52
|
15.40
|
7.20
|
7.00
|
|
[Co(CSPB)2(H2O)2]
|
C36H38N8O6Co2+
2(H2O)
|
772.93
|
72
|
55.89
|
55.81
|
5.43
|
5.40
|
14.49
|
14.40
|
7.62
|
7.55
|
|
[Ni(CSPB)2(H2O)2]
|
C36H38N8O6Ni2+
2(H2O)
|
772.69
|
72
|
55.91
|
55.83
|
5.43
|
5.35
|
14.49
|
14.38
|
7.59
|
7.50
|
|
[Mn(CSPB)2(H2O)2]
|
C36H38N8O6Mn2+
2(H2O)
|
768.93
|
70
|
56.18
|
56.09
|
5.46
|
5.39
|
14.56
|
14.45
|
7.14
|
7.05
|
|
[Zn(CSPB)2 (H2O)2]
|
C36H38N8O6Zn2+
2(H2O)
|
779.39
|
62
|
55.43
|
55.35
|
5.39
|
5.30
|
14.37
|
14.25
|
8.39
|
8.30
|
Another
noticeable difference is that the bands due to the COO- anion at
1600 com-1 in the IR spectrum of the each metal complex. The band at
1400 cm-1 in the IR spectrum of CSPB assigned to in plane OH
determination 16-18 is shifted towards higher frequency in the
spectra of the metal complex due to the formation of metal oxygen bonds. This
has been further confirmed by a weak band at 1105 cm-1 corresponding
to C-O-M stretching 16-18. Thus all of these characteristics
features of the IR studies suggested the structure of the metal complex as
shown in scheme-1.
Table-2
Magnetic Moment and Reflectance data of the Metal Complexes
|
Complex
|
Magnetic Moment
μeff(B.M)
|
Absorption band
(Cm-1)
|
Transitions
|
|
Cu-CSPB
|
2.14
|
24635
14771
|
C.T
2B1g→2A1g
|
|
Ni- CSPB
|
3.27
|
22460
14970
|
3A2g→3T1g (P)
3A2g→3T1g (F)
|
|
Co- CSPB
|
4.79
|
22990
17197
8870
|
4T1g (F)→4T2g (F)
4T1g (F)→4A2g
4T1g (F)→4T2g (P)
|
|
Mn- CSPB
|
5.19
|
23815
17811
15850
|
6A1g →4T1g (4Eg)
6A1g →4T2g (4G)
6A1g →4T1g (4G)
|
|
Zn- CSPB
|
Diamagnetic
|
--------
|
---------
|
Table-3
Antifungal Activity of Ligand CSPB and its metal complexes
|
Sample
|
Zone of inhibition of
fungus at 1000ppm (%)
|
|
PE
|
BT
|
N
|
T
|
RN
|
|
( CSPB)-Mn2+
|
75
|
62
|
59
|
55
|
49
|
|
( CSPB)-Co2+
|
70
|
67
|
69
|
70
|
60
|
|
( CSPB)-Ni2+
|
65
|
63
|
50
|
61
|
75
|
|
( CSPB)-Cu2+
|
85
|
50
|
48
|
85
|
83
|
|
( CSPB)-Zn2+
|
75
|
54
|
55
|
76
|
60
|
|
CSPB
|
63
|
80
|
85
|
69
|
70
|
PE=
Penicillium expansum, BT= Botrydepladia thiobromine, N=Nigrospora
sp., T= Trichothesium sp. RN= Rhizopus nigricum
Examination
of data of the metal content in each compound revealed a 1:2 metal:ligand (M:L)
stoichiomery in all of the complex of divalent metal ions. Magnetic moment
(μeff) of each of the metal complex is given in Table-2.
Examination of these data reveals that all complexes other than that of Zn2+
are paramagnetic while those of Zn2+ are diamagnetic.
The
diffuse electronic spectrum of the [Cu(CSPB)2(H2O)2]
metal complex shows broad bands at14771 and 24635 cm-1 due to the 2B1g→2A1g
transition and charge transfer, respectively suggesting a distorted octahedral
structure19-20 for the [Cu(CSPB)2 (H2O)2]
complex. Which is further confirmed by the higher value of μeff of
the [Cu(CSPB)2 (H2O)2] complex. The
[Ni(CSPB)2(H2O)2] complex gave two absorption
bands at 14970, 22460 corresponding to 3A2g → 3T1g
(P) and 3A2g → 3T1g (F)
transitions. The [Co(CSPB)2(H2O)2] complex
gave three absorption bands at 22990, 17197 and 8870 cm-1 corresponding
to 4T1g(F)→ 4T2g (F), 4T1g
(F) → 4A2g , 4T1g(F)→ 4T2g
(P) transitions. The diffuse, reflectance spectra and the value of the
magnetic moments (μeff) indicate an octahedral configuration
for the [Ni(CSPB)2(H2O)2] and [Co(CSPB)2(H2O)2]
complex. The spectra of [Mn(CSPB)2 (H2O)2]
shows weak bands at 15850, 17811 and 23815 cm-1 assigned to the
transitions 6A1g → 4T1g
(4G), 6A1g → 4T2g (4G) and
6A1g → 4T1g (4Eg)
respectively suggesting an octahedral structure for the [Mn(CSPB)2
(H2O)2] complex. As the spectrum of the [Zn(CSPB)2(H2O)2]
is not well resolved, it is not interpreted but it’s μeff value
shows that it is diamagnetic as expected.
CONCLUSION:
The
antifungal activity of all the compounds measured for various plant pathogens.
Inspection of the result shown in Table-3 indicates that all compounds are good
toxic for fungi. Out of all the compounds copper chelate is more toxic than
other. These compounds almost inhibit the fungi about 70%. Hence produced metal
chelate can be employed as garden fungicides. Further work in the direction is
in progress.
ACKNOWLEDGEMENT:
The
authors are thankful to Kapadwanj Kalvani Mandal, and Principal Dr. A.J. Raval
for permitting me to carry out the research work and for providing the library
and laboratory facilities.
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